Fault signaling system



Dec. 23, 1952 v w H T HOLDEN 2,623,108

' FAULT SIGNALING SYSTEM Original Filed Aug. 31, 1950 2 SHEETS-SHEET l D/ AL TONE BUSY TONE AGENT Dec.. 23, I952 WI'H. "r. HOLD N 2,623,108

FAULT SIGNALING SYSTEM Original Filed Aug. 31, 1950 2 SI-IEETS-S I-IEET 2 f To MAR/(E1? l CONNECTOR lNl/ENTO/P W H. 7. HOLDEN AGENT FIG. 2

Patented Dec. 23, 1952- UNITED STATES eater rice t'o Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Original applicati n August 31, 1950, Serial 182,468. Divided and this application Novemher 14, 1951', Serial No. 256,264

lhis application is a. division of ap 'ilication Serial No. 182,468 of W. H." T. Holden, filed August 31, 1950.

This invention relates generally to signaling systems and more particularly to' arrangements in such systems for detecting, ccunting, and registering signal impulses. z

The main object of the present invention is the improvement of such detecting, counting and registering arrangements, particularly with reference to the rapidityofresponse to signal impulses and to' the reliability of operation in response to such impulses.

In present-day signaling systems, such as may be useful with automatic telephone systems for instance; continuous j improvement is bein sought to increase the sp'eed'of response and to improve the reliability of circuits used for detecting, counting, and registering signals. In

the telephone art n particular, continuous effort is expended towards devising and developing circuits which will respond moreaccurat'ely and more reliably'at' a rapid rate to signals, such for instance as dialpulses'or'thelike.

The present invention, while not necessaril restricted thereto as regards its utility or scope, finds ready applicationin'aut o'matic telephone systeins'where apparatus and circuits are necessary to accomplish thesep'ul sede'tection, counting, and registering functions. An exemplary embodiment of the present invention is shown herein as capable of' being incorporated in an automatic telephonesystem" of the cross-bar type, such as that disclosed in Paten't 2,585,904 to A. J. Busch of February 19,1952; A skeletcnized disclosure of the system shown in the Busch disclosure is set forth in Patent 2,616,974 to J. W. Dehn of November', 1952'. TheDehn disclosure shows details of anoriginatin'g'register circuit of the cross-bar'system, whichcircuit is comparable in contextand function to the disclosure herein chosen as'an exemplary embodiment of the present invention.

The function of an originating register, among others, in the1cross-bar system' disclosed by Busch and Dehn, is to receive, to detect, to count, and to register dial pulse digits transmitted thereto under the controlof a callingsubscriber during the initiation by ,thelatter of a request fer a telephone'connection. v,

An object of the present invention'is theimprovement of such circuitry astheabove-menticned originating registericircuits regard to the reliability of theiun'ctioning thereof and the, rapidity of response thereby to signal impulses.

Claims. (Q1. 177-4311) A specific object of the present invention is the provision of improved circuit means for enabling such circuits .to be self-checking with regard to the accuracy and reliability with which they respond to signal impulses.

The present invention contemplates means for detecting impulses, ache-in of electron discharge devices for counting these impulses underthe control of the detecting means, and particularly means for checking the response of thecounting chain to said impulses. The counting chain is arranged to he stepped from device to device along the chain in response to impulses of a series such that at the end of. such a series the last device activated represents the pulse count of the series. Means isprovided for recyclingthe chain at the end of each series of impulses in preparation for counting the pulse content of a succeeding .series- A-- check circuit is provided for detecting the failure ofanydevice in the counting chain to be activated when it is supposed to be activated'in response to an impulse. 'Ihis circuit comprises a group of electron discharge devices which cooperatewith each other, withthe impulse detecting means, and with the counting chainto measure a time delay. Signal means-is energized through the-agency of said group of devices if thedevices in the counting chain do not respond properly to impulses within the said delay time. The present invention is in the nature of an improvemehtover a similar check circuit arrangement disclosed and claimed in Patent 2,609,498 to A. E. Bachelet and F. K. Low of September 2, I952. V

The check circuit more particularly comprises an electron dischargedevice which is energized responsive to each pulse, a second discharge device, energizedrespo'n's'ive to th energization of saidfirst device but after a time delay, and a third discharge device energized if thecou'nting chain properly advances in response to. each pulse therebyto dee'n'ergizei'said first deviceand thereby to prevent the energization of said secand device. These devices are arranged such that if said third device'isinot energized within a specified period of time} towindicfate the proper advance of thefcountingchain; then said first device is not deenergized, whereupon said second device will be energized after a measured time delay to sound an alarm indicative of trouble.

The present disclosure shows'in!proved circuit ineans for transferring the pulse counter a series of impulses countedby 'chain' of electron discharge devices or the like from the counting chain to registering means for storage pending the counting of other series for like storage or pending the usage of such registration by some other circuit. Registering means is provided for each series of impulses and such means are controlled jointly from the counting chain and from a steering circuit which determines into which register a particular series of counted impulses shall be registered. Each register is provided with a plurality of storage devices which may be energized or activated on a selective basis to indicate the pulse content of a series of impulses. The pulse counting chain is electrically connected through voltage responsive first gating means to all devices of all registers. The steering circuit is connected electrically to all such devices through second voltage responsive gating means. A storage device will become activated or energized only when both gates associated therewith are properly affected by suitable voltages derived jointly from the counting chain and from the steering circuit. This latter subjectmatter is disclosed and claimed in application Serial No. 182,468 of W. H. T. Holden, filed August 31, 1950, which application is the parent of which this present application is a, division.

The invention, outlined above, will be explained with the aid of the following detailed disclosure of the exemplary embodiment thereof, the drawings forming a part of such disclosure being described generally as follows:

Fig. 1 shows the pulse receiving, detecting, and counting circuits of a cross-bar originating register circuit embodying the invention; and

Fig. 2 shows the registers and steering circuits of the originating register embodying the invention.

General description The present invention is herein disclosed as embodied in circuits which may be used in an automatic telephone system such as is disclosed in the above-mentioned Busch disclosure. Busch discloses in detail a cross-bar system wherein originating register circuits are used for transmitting dial tone to calling subscribers, detecting and counting pulses of called digits, registering these called digits, and seizing an idle marker circuit for the purpose of having such a marker complete the desired connection. Since the present disclosure of the invention relates particularly to the pulse detection, counting, checking, and registering functions of an originating register, details other than of such circuit may be obtained from the Busch or Dehn disclosures.

As may be obtained from the Busch or Dehn disclosure, the general sequence of events during the originating of a call by a subscriber is as follows:

(1) The calling subscriber lifts his receiver thereby seizing an idle marker circuit and automatically informing the seized marker that a dial tone connection is desired;

(2) The seized marker tests for and seizes an idle originating register circuit;

(3) The marker interconnects the calling line with the seized originating register circuit over the cross-bar switch train and then the marker releases;

(4) The originating register transmits dial tone to the calling subscriber;

(5) The calling subscriber dials the digits of the called number or other desired destination;

(6) The originating register receives, detects,

4 follows, and counts the pulses of each digit and registers such digit;

(7) When a sufiicient number of digits have been registered therein, the originating register seizes an idle marker circuit and transfers thereto, among other items of information pertaining to the call, the digits so registered; and,

(8) The marker, when it has received all of the information from the originating register, releases the originating register, completes the call, and then releases itself.

Since the present invention is described herein as embodied only in circuits of an originating register, the subsequent detailed description will not cover items (1), ('7) and (8) above. Such matters, however, are fully disclosed by Busch and Dehn and are not necessary to the present description.

Detailed description Hereinafter whenever a part of the drawing is referred to by its reference character, such as the off-normal relay ON(1), the designation ON refers to the reference character which identifies the part on the drawing, and the designation (1) refers to the figure of the drawing wherein that part is located. Thus the designation of relay ON(1) means the relay marked ON on Fig. 1, etc.

Seizure of originating register When the marker seizes an idle originating register circuit, such as is disclosed partly in Figs. 1 and 2, the off-normal relay ON(1) thereof is operated by the marker. This relay ON(1) will remain operated as long as the register circuit is being used or until the register is released prematurely for one of a number of possible reasons.

Interconnection between calling subscriber and originating register After the seizure by a marker of an idle originating register circuit, the marker effects an interconnection over the cross-bar switch train between the seized register and the calling line, thereby closing the ring and tip conductors I08 and lill of the register over the calling line loop. The line relay L(l) is operated in a circuit extending from ground, over contact I of the dial tone relay DT(l), contact 2 of the busy tone relay BT(1), left winding of relay L(l), tip conductor I91, over the switch train and the line loop, back over the ring conductor I00, right winding of relay L(l), to negative battery. (It is to be understood that whenever a voltage is indicated as negative or positive it is to be assumed that the opposite pole of the source is grounded unless otherwise designated or mentioned.)

Relay L(l), upon operating on the initial line loop closure performs three function as disclosed:

(1) The slow-to-release relay S(1) operates in a circuit from negative battery, through the Winding of relay 3(1), through resistance [62, contacts I and 2 and armature of relay L(l), to positive battery. The relay S(1) is energized each time that relay L(l) is operated (closed line loop) and is permitted to start releasing each time relay L(l) is released (open line loop periods representing pulses of a digit). The slowrelease characteristic of relay S(1) assists in making sure that relay S( 1) does not release during the release time of relay L(l) representing pulses of a digit. There is another circuit phenomenon which further assists relay 3(1) in remaining operated during the release time of relay L(l). Such phenomenon will be described presently.

(2) Condenser CH1) acquires a charge in a circuit extending from positive battery (130 volts positive for instance), over contact 2 of relay L(l), armature of relay L(l), resistance [03, to ground through condenser Cl (1). Condenser Ci (1) acquires a positive charge upon its upper plate each time relay L(l) operates. This voltage will be approximately full battery potential (+130 volts). As will be described in detail hereinafter, this charge on condenser CH1) is used as the pulsing source for controlling the counting chain and control tubes when relay L(l) releases in response to' each open line loop pulse.

(3) Positive battery potential is applied over contacts 2 and i and armature of relay L(l), over conductor 1% to the circuits associated with the gas tubes RAG) and REG). Tubes RA(1) and'REu) are normally extinguished and thereforetheir cathodes K are at negative battery potential (say 5() volts with respect to ground). Positive battery potential applied to conductor its starts the charging of condensers Ida and 1%- in parallel circuits extending from conductor through resistances ii)? and H38, condensers W5 and let, resistances W9 and Nil, to negative battery. The rectifiers, such as rectifier REZU) in shunt of resistance it], have little if any effect upon the charging time of the condensers because the rectifiers are so poled as to represent relatively high impedances when the voltage at their arrows is negative with respect to the other terminal. (These rectifier'units will be encountered throughout the discussion and it is to be understood that when the arrow terminal is more positive than the other terminal, these units represent low impedances and will pass large currents readily; however, as has been mentioned, when the voltage polarity is reversed, these units represent high impedanc'es which however are finite-not open circuits.) The time constant of the charging circuit for condenser is longer than that for condenser H65; therefore, assuming that they are permitted to charge up at will, condenser H35 will acquire a sufficient- 1y positive voltage on its left terminal, with respect to negative battery, to fire tube RA(1) befor tube REG) is fired by its condenser Hit. This time difference is important with regard to subsequent discussion. The time constants are arranged such that tubes RAM) and RE(1) will both fire if relay L(l) remains operated long enough to represent the pause between digits (interdigital time) and will thus probably fire upon the long pause between the first operation of relay L(l) and the first pulse of the first digit.

When tube RAG) fires, by virtue of condenser iiis having acquired sufiicient voltage upon its left plate to break down the starter gap SK, tube RAG) will pass a surge or" ourrentwhich will by-pass the anode resistance ill through condenser H2 which acts as a shortcircuit under the transient condition. This current surge passing through the cathode resistance ta raises the potential at the" cathode K of tube RAH) about 100 volts more positive; that is, to about +50 volts with respect to ground. This pulse is applied to conductor H 3 for purposes to be explained later. Very shortly, however, the condenser H2 becomes charged and loses its shunting eiiect thereby causing the anode potential of tube RAG) to drop; This drop of anode potential in conjunction with the rise in cathode potential willextinguish tube RA(1). Iube RAG) will not sustain another discharge until condenser H2 has dissipated its charge through resistance I H and unless relay L(l) remains operated to recharge condenser 1%. If relay L(l) remains operated for a sufiiciently long time tubeRAfl) will refire at regular intervals thereby providing volt pulses at its cathode K over conductor H3. This initial application to conductor H3 of pulses of about 100 volts magnitude positive with respect to negative 50 volts (that is, +50 volts) has no effect upon the other circuits as will be appreciated from subsequent discussion.

Similarly, when tube REG) fires, 2. +50 volt pulse is applied to conductor IM from the cathode K of tube REG). Tube REG), like tube RAG), is self-extinguishing by virtue of the condenser H5 shunting the anode resistance I It. The pulses applied to conductor H4 by tube REG), as will be explained hereinafter, will fire the start tube 837(1) of the pulse counting chain but have no other efiect at this time.

It will be observed that when relay L(l) is released for any reason, the condensers Hi5 and 5 will lose their accumulated charges in parallel discharge circuits froninegative battery, resistances t9 and Ht, condensers Hi5 and H35, rectifiers RE2(1) and REM (1), conductor iii i, resistance I92; to negative battery through the winding of relay 53(1) By virtue-of the'fact that the positive charges-on condensers W5 and IE6 find rectifiers RE2(1) and RE22(l) low impedances for the discharges-the discharge times are always shorter than the-charging times thus precluding the possibility of condensers I and [9t integrating short pulses. That is; condensers Hi5 and 1% will always start timing'from the same reference level of timeand charge. Furthermore, these discharge currents will assist relay 8(1) in remaining operated during the release of relay L(l) representing open line loop pulsing periods.

Upon the operation of relay 3(1), above described, a circuit iscompleted for operating relay ON! (1) from ground, over the contact of relay 8(1), the contact-of'relay ON('1), to negative battery through the winding'of relay'ONHl). This ground extends to the sleeve of the switch connection over the'dotted path H1 to hold the connection. Relay ON! (1), uponoperating-applies positive battery (say 130 volts) over its contact to conductor 264 which supplies plate-voltage to the tubes as Will be described.

When relay ONi (1) operatesit firesthe gas tube GL(1) in an obvious circuit. The tube GL(1) is continuously energized, as long as relay ON! (1) is operated, for the purpose of providing continuous light for keeping the rest of the gas tubes in the circuits energized so they will-fire promptly and reliably. This, as Will be obvious, is a well known keep alive means used extensively in gas tube'circuits.

Upon the operation of relayONHl), positive anode voltageis supplied to the main anode of the start tube ST(1) of thecounting chain (tube ST(1) through tube 0(1) of Fig. 1) over conductor 204, through the left primary winding of transformer T(l), and over conductor 1 E3. Tube ST(1) is normally extinguished thereby setting its cathode at 50 volts potential. When tube REG) applies the first IOU-volt pulse (+50 volts) to conductor W3, this pulse is applied to the starter electrode of tube ST( from conductor [it over contact 5 of relay BT(1) to tube ST(1). This pulse-of +50 volts raisesthe starter'electrode of tube ST(1) some volts-positive with 7 respect to the cathode and thereby fires tube ST(1). A surge of current passes to negative battery, through condenser H9 in shunt of the cathode resistance I20, across the main gap of tube ST(1), over conductor H8, through the left primary winding of transformer T(1) from positive battery on conductor 204. The presence of condenser H in shunt of resistance I20 comprises efiectively a short-circuit across resistance I20 during the surge transient. This insures that the cathode of tube ST(1) will remain at a negative 50-vo1t potential for a delay time determined by the time required to charge up condenser IIO. This delay time is used throughout the counting chain, as will be obvious from an inspection of the repetitive nature of the cathode circuits, for a purpose to be mentioned later. Eventually condenser I E0 will become charged to the steady state cathode potential which will be approximately +50 volts. This potential is insufficient to fire the gas diode DST(1) connected between the cathode of tube ST(1) and the starter electrode of tube Hi). It will be noted that when tube 83TH) was fired, condenser I31 was also included in a time delay charging circuit extending from negative battery, through the cathode resistance of tube PG(1), pulsing conductor I35, condenser iS'i, resistance I36, to the top of resistance I20, which, as has been explained, is attempting to rise to about +50 volts. If the condenser I I 9 were not present, condenser I31 would delay the rise or the +50 volt potential at the left electrode of the diode DSTO) a length of time necessary to charge condenser I31 to this newly applied potential. Then the delay caused by the charting of condenser I31 could be used for the same purpose as condenser I I9 as far as preventing the instant firing of diode DST(1) is concerned. The circuit, as shown, is arranged such that the time element represented by the combination of condenser I E0 and resistance I20 is of the longer and controlling duration, although it should be remembered that condenser I31 does represent a time delay in the application of the +50 volt potential to the left electrode of tube DST(1).

The current surge through the left primary winding of transformer T(1) will induce a voltage in the secondary Winding which will fire the check tube 031( Tube CK(1) upon firing, raises its cathode to about +50 volts for a purpose to be explained hereinafter. It will be obvious that any further pulses from tube REG) over conductor H0, assuming that relay L(1) is still initially operated, will have no further efiect upon tubes STU) and CKG).

When relay ONI (1) operated, positive battery was applied over conductor 204, through the retard coil LI(1), to the main anode of the gas tube ON2(1). This positive potential is also applied to the starter electrode of tube ON2(1) from conductor 204, through resistance I2I, condenser I22, and resistance I43. This fires tube ONZII). Before tube ON2(l) fires, its cathode and thus conductor 202, is at approximately -50 volts and the dial tone relay DT(1) is released due to the fact that no current is flowing in the cathode resistance I23. When tube ON2(1) fires, its cathode remains temporarily at about negative 50 volts, by virtue of the condenser I24 shunting the cathode resistance I23 as previously explained, and then rises to about +50 volts when condenser 24 becomes charged. The voltage drop across resistance I23 thereupon operates relay DT(1). Relay DT(1), upon operating, applies dial tone over its contact 2, contact 2 of 8 relay BT(1) to the tip side of the line through the left winding of the line relay L(1).

Upon hearing dial tone, the calling subscriber may begin to dial the digits of the called subscribers number, or other called destination.

The pulse generation and check circuits A pulse is transmitted by an open line loop and is detected in the originating register by means of relay L(1) which releases for each pulse.

When relay L1) releases, the charge on condenser CI(1), which is in the neighborhood of +130 volts, will be discharged in the circuit including condenser CI (1), resistance I03, contacts 3 and 4 and armature of the relay L(1), resistance I24, to ground through the parallel network of resistance I25 and condenser I26. The presence of condenser I20 will delay the effect of this pulse at the starter electrode of tube DP(1) until condenser I20 becomes charged. The positive pulse will be effective to fire tube DP( 1) which will cause a current to fiow from positive battery on conductor 204, across the main gap of tube DP(1), to negative battery through the cathode resistance I27. The cathode of tube DP(1) will be raised to about volts, which -volt rise is transferred through condenser 02(1) to the cathode of the check tube CK(1). The cathode of tube CK(1) will temporarily be raised an additional 100 volts above the +50 where it was thereby causing the tube CK(1) to be extinguished by this cathode commutation. As soon as condenser 02(1) loses the charge it acquired from the cathode of tube DP(1), the cathode of tube CK 1 will revert to about --50 volts potential to prepare tube CK(1) to be refired as will be described.

As has been described hereinbefore, when relay L(1) releases, the firing condensers I05 and I06 of tubes RA(1) and RE(1) are discharged and relay 8(1) remains operated.

The positive pulse from condenser CI(1), in addition to firing tube DP(1) as above described, is applied to the starter electrode of the trouble tube TR.L(1) through a time delay circuit. Condenser I28 begins to acquire a charge in a circuit from the positive potential on condenser CI(1), through resistance I03, contacts 3 and 4 and armature of relay L(1), resistances I24 and I29 and I30, condenser I28, to negative battery through the winding of the busy tone relay BT(1) This pulse applied to the tube TRL(1) to fire same is of course also delayed for the additional time required to fire tube DP(1). As soon as tube DP(1) fires, then condenser I20 will continue to acquire a charge due to collector voltage accumulating at the starter electrode of tube DP(1). If condenser I20 is permitted to charge up for a sufiicient length of time to fire the trouble tube TRL(1), then relay BT(1) will be operated. If relay BT(1) operates, it opens at its contact 4 the circuit for firing the start tube STU) of the counting chain, it closes a circuit over its contact I for sounding an alarm and for locking the register busy so it may be tested, and relay BT(1) closes a busy tone signal over its contact 3 to the tip IOI of the line through the left winding of the line relay L(1) to inform the calling subscriber to disconnect and to try again. As will be appreciated from description to follow, if the circuits of the originating register function properly tube DP(1) will be extinguished to permit condenser I28 to discharge through rectifier I 9 REI(1) to ground through resistances I29 and I before tube, TRL(1) can be fired.

When tube DP(1) was fired thus raising its cathode about 100 volts positive from negative battery (about -50 volts), this positive 100-volt pulse was applied to the starter electrode circuit of the pulse generation tube PG(1) as a charging source for condenser I3I through resistance I32. This charging circuit incorporates a delay between the time when the pulse is produced at the cathode of tube DP(1) and the time when the tube PG(1) will fire. It will be recalled that when the check tube CK(1) was fired initially upon the initial firing of the start tube ST(1), a 100- volt pulse was produced at the cathode of tube CK(1). The delay circuit built into the starter circuit of tube P'G(l) is sufficient to prevent tube PG(1) from firing on this initial pulse transferred from the cathode of tube CK( 1) through condenser CZ 1), until the initial charge on condenser 02(1) has been dissipated through resistances l2? and IE3. After a delay interval of some 7 to 3 milliseconds, tube PG(1) will fire thereby raising its cathode from about +50 volts to about +50 volts (100 volts positive). Tube PG(1) is self-extinguishing, as were tubes RAG) and REG) as soon as condenser I34 in the anode circuit of tube PG(1) acquires its charge. The net effect, therefore, is that a positive 100-volt pulse is applied from the cathode of tube PGQ) to the pulsing conductor I35.

It will be recalled that the start tube STU) was fired and is conducting. Due to the conduction through tube ST(1) under steady state conditions, the cathode of tube ST(1) will be at about +50 volts. This, as will be remembered, was insufficient to fire the gas diode DST(1) interconnecting the cathode of tube ST(1) to ground through resistances I36 and I 38. However, when the pulsing conductor I 35 is raised positively 100 volts, the gas diode DST(1) will be fired through condenser I38. The resistance I3! will cause a positive voltage pulse to appear at the starter electrode of tube I (l) as a result of the current surge therethrough when the diode DSTG) is fired. The relative magnitudes of resistances I38 and I36 are such that the voltage produced across resistance I38 when tube DS'I(1) fires, is due mostly to the pulse from condenser I31 and very little from the direct-current circuit connected to diode DST(1 This pulse will fire tube 5(1). Due to the presence of condenser I385 across the cathode resistance I49 of tube I01), the cathode of tube I(l) will be retained at about -50 volts for a short interval of time to insure that the gas diode DI(1) is not fired from the pulsing conductor I35. Eventually, when condenser I39 becomes charged, the oathode of tube l(l) will rise to about +50 volts to prepare the diode 135(1) to be fired on the next pulse on conductor I35 from the pulse generation tube PG(1). This counting chain interaction arrangement is disclosed and claimed in Patent 2,616,627 to W. H. T. Holden of November 4, 1952.

The current surge through the left primary winding of transformer T(1), caused by the firing of tube l(l), will cause the anode voltage at tube ST(1) to drop negatively. This drop of anode voltage at tube ST(1) in conjunction with the fact that condenser Hi9 retains the cathode at about +50 volts for a short time will extin guish tube ST( 1) by anode commutation, Subsequently, tube STU) assumes a steady state non-conducting condition whereunder its cath- 10 ode resumes its volt potential such that tube I(1) will not refire after it is extinguished unless tube ST(1) is conducting.

The surge of current through transformer T(1) refires tube CK(1) as previously. By cath-- ode commutation through condenser C2( 1), tube CY(1) in firing, extinguishes tube DP(l) which in turn allows condenser I28 to discharge before tube TRL(1) can fire. This reverts the pulsing and check circuits to normal awaiting the next operation and release of the line relay L(l) representing the next pulse. As soon as relay L(l) reoperates at the end of the first pulse, relay 5(1) is reenergized, condenser CI (1) is recharged, and the timing circuits of tubes RAM) and REG) are started for timing the interdigital pause.

Counting initial digit of one pulse An initial digit of one pulse, unless followed directly by a second digit of one pulse as will be explained, is assumed not to be a legitimate signal, because of the frequency with which such erroneous indication may be efiected by accidental manipulation of the subscribers dial, by spurious electrical impulses, etc. Such an ini tial digit is absorbed on the basis of the above assumption; but, as will be explained, it is not discarded in view of the fact that a second digit of one pulse is presumed to indicate a legitimate l1 prefix for a special code, such as a service code of 11X, where X may be any ligit from 2 to 9.

In discussing the action of the pulse counting chain, the special 11X circuits, and the steering and registering circuits it will be assumed that the pulse generation and check circuits operate normally so as to indicate the proper advance of the counting chain. Previous discussion is adequate for an explanation of trouble conditions. The normal functioning of the pulse detection and checking circuits, as will be apparent from previous discussion, effects the following conditions:

(l) Each time that the line relay L(l) releases and reoperates to indicate a pulse of a digit, a pulse of about IOU-volt positive nature is applied to the pulsing conductor I35; and,

(2) Each time that the line relay L(l) remains operated for a sufiicient time to represent an interdigital pause, tubes RA(1) and REG) fire in succession to apply one pulse each of about -volt positive amplitude to respective conductors H3 and II 4, the pulse on conductor H4 following the pulse on conductor I I3 by a timed period.

At the end of the first digit of one pulse, as above discussed, tube I(1) will be conducting and tube STU) will be extinguished. Due to the conduction through tube I(1), the upper terminals of the two gas diodes TDIEMI) and TDI I (1) connected to the cathode of tube I(l) will be set at +50 volts after a delay of time after the firing of tube l(1) necessary to charge condensers CM 1) and CM 1) to this newly applied potential. The lower terminals of tubes TDIll(1) and TDI-l 1) are connected over respective conductors are and 2H in parallel to ground through resistances 2693 and 209 and through respective condensers 2% and 207 to the upper terminals of respective gas diodes TDAEHZ) and TDAI (2) of Fig. 2 associated with the A digit register tubes A.G(2) to A(7).

The diodes TDAMZ), TDAHZ), TDAMZ). TDAMZ), and TDA'l (2) are all controlled, as regards the potential on their upper terminals,

11 from the cathode of the A digit steering tube A(2). With the tube A(2) non-conducting, its cathode, and thus the upper terminal of the A register diodes, is at negative battery potential (50 volts) from conductor 203. The only time that a register tube, such as tube A(2), or Al (2) can be fired to register a digit is when the two diodes, such as TDIO(1) and TDII(1), associated with a counting tube, such as tube 12 PPD(1). The common connection between rectifiers RE3(1) and RE4(1) will, due to the polarity of such rectifiers, assume the most negative potential of the respective arrow terminals. At the end of the first digit of one pulse both cathodes of tubes H1) and ON2(1) are at +50 volts and thus the left terminal of the diode PPD(1) will be at +50 volts. The 100-volt positive pulse on conductor H4 from tube RE(1) will thus fire I(1), can fire in cascade with two corresponding the gas diode PPD(1) and th latter, through tubes, such as diodes TDAMZ) and TDAl(2) the agency of the current surge in resistance I54, or TDBO(2) and TDBI(2), etc., or TDGIKZ) will fire the tube PP(1). The condenser I55 and TDGI(2), associated with a particular shunting the cathode resistance I56 of tube group of register tubes. This condition exists PP(1) holds the cathode of tube PP(1) at 50 only when the associated steering tube, such as volts long enough to prevent the firing of tube tube M2) is conducting and when the asso- (1) on the first pulse from tube REG). Evenciated counting tube, such as tube H1) is contually condenser I55 becomes charged and the ducting. When a counting tube, such as tube cathode of tube PP(1) rises to about +50 volts H1) is conducting, the 100-volt positive pulse to condition the diode DH (1) so that it will fire from the tube RA(1) over conductor I I3 will tube (1) on a second digit of one pulse. fire both associated diodes, such as diodes In addition, when tube RE(1) generates the TDIO(1) and TDII(1), because the 100-volt interdigital pulse on conductor II4, the start pulse will drive the upper terminals of the diodes tube S'I(1) is refired over the contact 4 of reto about +150 volts which is sufficient to fire lay BT(1). The resulting current surge through them since their lower terminals are returned tube STU), as has been explained, extinguishes to ground over conductors 2H! and 2H and the tube I(l) by anode commutation and the through resistances 208 and 209. The resulting circuits are ready to receive the next digit. pulse of about +100 volts developed across these It will be observed that none of the steering resistances 208 and 209 will attempt to fire all tubes, such as tubes A(2) to H(2), have been register tube diodes, such as TDAO(2) and operated in response to the first digit of one TDAI(2), TDBO(2) and TDBI(2), etc., TDGO(2) pulse and that, although this first pulse has is insufficient to fire these diodes however, unbeen absorbed by the firing of tube PP(1), the less they have been enabled by having their first pulse has not been discarded. upper terminals raised to volts from 50 Furthermore, it will be seen that the abovevolts by the associated conducting steering tube, described means for transferring the pulse such as tube A(2). In the present instance, regcount from the counting tubes of Fig. 1 to the ister tube diodes TDAO(2) and IDAI(2), as register tubes of Fig. 2 involves two gas diodes well as the corresponding diodes of other regisfor each counting tube, such as diodes TDII](1) ter groups, will not be fired because the assoand TDII(1) for counting tube I(1). These c ed Stee t are non-Conducting. Thus diodes, under proper conditions as have also been the pulse generated by tube RA(1) is not effecindicated, will fire two-out-of-five register tubes, tive to register the first digit of one pulse. As such as tubes A0 (2) and AI(2). This two-outsoon as the pulse from tube RA(1) ceases, the of-five code is well known and is arranged as and TDGHZ), associated therewith. 100 volts follows:

Digit Oountingrgrlagn Diodes Registerlhl tlae Diodes Rcgislticlrcgubcs TD10(l)'lD11(l) TDAO(2)TDA1(2) A0(2)Al(2) TD20(1)TD22(1) TDAO(2)-TDA2(2) A0(2)A2(2) TD3l(1)TD3 TDAl(2)--TDA2(2) Al(2)A2(2) TD40(1)TD44(1) TDAO(2)TDA4(2) AO(2)-A4(2) 'ID5l(1)-TD54(1 TDA1(2)-TDA 2) A12)A4(2) TD62(1)TD64(1) TDA2(2)TDA4(2) A22 -A4 2 TD(1)TD77( TDAO(2)TDA7(2) A0(2)-A7(2) 'r sun-rnsvu) TDA1(2)TD 7(2) Al(2)-A7(2) 'lD92(l)-TD97(1) TDA2(2)TDA7(2) A2(2)-A7( TD104(1)TD107(1) TDA4(2)TDA7(2) A4(2)-A7(2) diodes, such as TDIIKI), TDII(1), TDAO(2) and TDAI(2) which may have fired are extinuished.

A short interval after the pulse on conductor II3 from tube RA(1), tube REM) generates a -volt positive pulse on conductor H4, as has been described. The gas diode PPD(1) in the starter electrode circuit of tube PP(1) is controlled from three quarters. The pulsing conductor II I from tube RE(1) is connected thereto through condenser 5|. Also, the cathode of tube H1) is connected thereto through the resistance I52 and rectifier RE3(1). Furthermore, the cathode of tube ON2(1) is connected thereto through the resistance I53 and rectifier REMI). The right terminal of the gas diode PPD(1) is at ground potential through resistance I54 and therefore it will require a pulse of at least 100 positive volts to fire. t di de Counting a second digit of one pulse If a second digit of one pulse is received and counted by the originating register circuit, it is assumed that this is a legitimate indication of an 11 prefix to a special code, such as a special 11X code of a service nature.

When relay L(1) releases on the first pulse of the second digit, the pulse generation tube PG( 1) again produces a positive 100-vo1t pulse on the pulsing conductor I35. This pulse fires tube I(l) which extinguishes the start tube ST(1) by anode commutation. Again, since tubes ON2(1) and I(l) are both conducting, the left terminal of the gas diode, PPD(1) is raised to +50 volts. Since tube H1) is energized, the upper terminals of the gas diodes TDIO(1) and 'I'DI I (l) are again raised to +50 volts.

When relay L( 1) reoperates at the end of the first pulse and remains operated to indicate the time delay between digits, tube RAll) fires .to produce a 100-volt positive pulse on conductor H3. This pulse will, as before, fire the gas diodes TDl(1) and TDI l (1) associated with the cathode of counting tube (1). However, since the steering tube A(2) of Fig. 2 has not been energized, the digit one, represented by the firing of the diodes TDlil(1) and TDli(1), will not be registered in the A digit register tubes Ail(2) and Al (2).

Subsequent to the firing of tube RAG), tube REG) fires to produce on conductor EM a 100- volt positive pulse. By virtue of the fact that tube PP(1) is conducting, as has been explained, the cathode thereof, and thus theleit terminal of the gas diode Dl l (l) is raised to +50 volts. The pulse on conductor I It will fire the diode Di H1) through condenser I57 thereby firing the tube li(l). The cathode of tube (1) will be raised to +50 volts thereby raising the potential of conductor 20! from 50 volts to +50 volts. The energization of conductor 2M is an indication that an 11 prefix has been detected and registered in the counting circuit. This indication is used in a manner presently to be described. When tube H (1) is fired it extinguishes tube PP(1) by cathode commutation through condenser E58.

Further detection of digits of one pulse each, whether intentional or not, will have the effect merely of alternating the conduction in tubes PP(1) and H(1). Timing circuit means (not shown) may be provided which, under this condition, will eventually call in a marker circuit for the purpose of switching the calling line to a permanent signal tone trunk to call in an operator for trouble analysis. Examples of such circuits are fully described in the Busch and Dehn disclosures abol' identified. Such circuit may also be used to in icate a total failure of the calling line to dial any digits at all or to indicate the receipt by the originating register of only one pulse followed by a continuous operation of the line relay 11(1). Other trouble conditions may be met by other known circuits but, since the present invention is not particularly concerned with such expedients, none of these circuit means is shown or described.

Counting and registering the X digit of an 11X code It will be assumed that, after the dialing of two digits of one pulse each, the calling subscriber dials a digit greater'than one pulse, such as three pulses, to indicate a special 11X code.

Upon the first release of relay L(l) ,the result- 1 lug pulse on conductor H35 fires tube 5 (1) ,thereby extinguishing tube STU). The second release of relay L(1) occurs before tubes RAG.) and REG) can fire and thus the second pulse on conductor I35 fires tube 2(1), thereby extinguishing tube 5 (1). When tube 2(1) fires, its cathode is raised to +50 volts thereby producing a G- volt positive pulse to the starter electrode of tube A2(l) over conductor 159. When tube A2(l) fires it extinguishes itself by virtue of the anode circuit arrangement of condenser its in shunt of the anode load resistance ltd, as has been discussed. Tube A2(l), upon firing momentarily, raises its cathode to about +50 volts and the resulting 100- volt positive pulse is applied through condenser M2 to conductor 282. Since conductor 2% was originally at +50 volts due to conduction through tube 0N2(l), the conductor 282 is now momentarily provided with a pulse extending to about +150 volts. This pulse will fire the gas diode DA(2) to in turn fire the steering tube A(2). Condenser 215 in the cathode circuit of tube A(2) will hold the cathode at volts for a short length of time and then will permit the cathode to assume a potential of about +50 volts. This +50 volt potential will enable the gas diode DB (2) to be fired by the next pulse on conductor from conductor H4 at the end of the next digit. This +50 volt potential from the cathode of tube A(2) also raises the potential of the upper terminals of diodes TDAMZ), TDAl (2), TDAMZ), TDAMZ), and TDAl(2) to about +50 volts such that this three-pulse digit will be registered in the A digit register tubes.

When tube A(2) fires, the surge of current through retard coil Li (1) over conductor 2% extinguishes tube ON2(1). Tube ON2(1), upon ceasing to conduct, releases the dial tone relay DT( 1).

Thus, it will be observed, digits may be registeredin the registers of Fig. 2 only after a digit of more than one pulse is counted by the counting circuits of Fig. ,1.

Relay L(1) will reoperate and release again before tubes RA(1) and REG) can fire thus pro ducing a third pulse on conductor i555. This pulse will fire tube 3(1) which in turn will extinguish tube 2(1) .At this juncture tubes A(2), 3(1), and il 1 will be operated. When relay L(1) releases at the end .of the three-pulse digit, tube RAG) fires to produce a -volt positive pulse on conductor H3. This pulse will fire gas diodes TDtl (l) and T1332 (1) associated with the conducting tube 3( 1). The firing of these diodes will create positive pulses across the resistances 2% and 2M5 re spectively of Fig. 2 due to passage of current therethrough from the diodes over conductors 2i i and 212. Since the upper terminals of the gas diode TDA|(2) and TDA(2) are at +50 volts due to conduction in tube A(2), the positive pulses across resistances 209 and 2m will fire these diodes, which, in turn, will cause surges of current in resistances 2i 1 and 2 i 8 to fire tubes Al(2) and A2(2). The tubes A!(2) and A2 2 will remain conducting to indicate the registration, on a two-out-of-five basis, of the digit 3.

Subsequent to the pulse from tube RAG) tube RE(1) fires to produce a 100-volt positive pulse on conductor H4. This pulse will refire tube ST(1), thereby extinguishing tube 3(1) to recycle the counting chain. This pulse will also be applied over conductor 2% to fire the diode DB(2) through condenser 2H2. The firing of diode DB(2) causes the B digit steering tube 3(2) to conduct and to extinguish tube A(2) by anode commutation through the agency of retard coil L|(l). The condenser 223 across the cathode resistance 225 of tube 13(2) holds the cathode at 50 volts long enough to prevent the firing of the diode DC(2) by the present pulse on conductor 265. Eventually, when the condenser 223 becomes charged, the cathode of tube 18(2) will rise to +50 volts. This rise of potential primes the diodes TDBEHZ), TDBHZ), TDB2(2), TBBQQ), and'TDB'HZ) for the B digit register so that two out of five of these diodes will be fired to register the next digit. When tube M2) was extinguished, the +50 volt priming potential was removed from the corresponding A digit register diodes so that the A digit register cannot be affected by subsequent digits.

On 11X codes it is the practice for th originating register to call in a marker circuit as soon as the X digit is registered in the A digit re is ter. The indication that such has taken place is the firing of the B digit steering tube B(2). It will be recalled that the conduction by tube i I (1) raised the potential of conductor 20! from +50 volts to +50 volts by virtue of the connection of the cathod of tube (1) to conductor Elli. When tube B(2) fires, its cathode raises the potential of conductor 226 from 50 volts to +50 volts. These two conductors 2i]! and 22B are connected to the top terminals of respective rectifiers R3(2) and R4(2). These rectifiers are arranged and poled such that their connected arrow terminals will assume a potential which is the more negative of the two potentials on conductors 20! and 226. If either or both of conductors 20! and 226 is at +50 volts, then the arrow terminals of rectifiers 133(2) and 114(2) will be at substantially 50 volts and tube EH2) will not fire. However, if both of conductors 20! and 226 are at +50 volts, as they will be under the present conditions of an 11X code (a code of 113 in the example), then the arrow terminals of rectifiers R3(2) and R4(2) will rise to about +50 volts and will therefore fire tube H! (2) through the rectifier RS(2).

When tube Hl(2) fires, it extinguishes tube B(2) by anode commutation and operates the marker start relay MST(2) Relay MST(2), upon operating, causes the seizure of an idle marker circuit for the purposes of completing the desired call, which, in the case of an 11X service code, may be to a suitable operator.

Regular seven-digit local call For calls which are directed to local subscribers, there will be no 11 prefix and the digits dialed may represent the familiar A, B, and C office digits followed by four station numericals. In this case the first digit will be greater than one pulse and thus will be registered in the A digit register. The

next six digits will be successively registered in the B, C, D, E, F and G registers. At the end of the registration of the G or seventh digit, tube H(2) will be fired thereby operating relay MST(2) to seize an idle marker circuit for the purpose of completing the desired connections. During this sequence of operation, the tube HI (2) will not be fired when the B digit steering tube B(2) conducts because conductor 20l will be at +50 volts due to the fact that tube i l 1) was not fired.

A zero operator call If the first digit dialed were the digit 0, representing ten pulses, the digit ten would be registered in the A digit register by the firing of register tubes A4(2) and A1(2). These two tubes would raise the potential of conductors 228 and 229, connected to their respective cathodes, from 50 volts to +50 volts. As was the case with the 11X codes, making conductors 20I and 226 both +50 volts, these two conductors 228 and 229 will increase the potential of the arrow terminals of rectifiers Rl(2) and R2(2) from 50 volts to +50 volts thereby to fire tube HI (2) and operate relay MST(2). This action seizes an idle marker after the first digit is registered for the purposes of switching the calling subscribers line circuit to an operator as desired.

Marker operation When an idle marker (not shown) is seized due to the operation of relay MST(2) the register tubes of Fig. 2 are connected to the seized marker over cable 230 for the purpose of transferring the registered information to the marker. The

- transfer is made by circuits in the marker which can detect which cathodes of which register tubes are at +50 volts. The marker is also supplied (by means not shown) with other information concerning the call, such as the location of the calling subscribers line circuit in the OfllCE plant, the class of service to which the calling subscriber is entitled, the nature of the call (11X call, zero operator call, etc.) etc. From this information the marker proceeds to supply the service requested,

While the invention has been disclosed herein by way of example as embodied in a circuit using cold cathode gas discharge tubes, it will be an obvious modification within the skill of the art to substitute hot cathode thyratrons for the cold cathode tubes, in order for instance to embody added speed of operation in the circuits.

Furthermore, with regard to the voltage responsive gates, which in the exemplary embodiment comprise gas discharge cold cathode diodes, it will be an obvious modification to substitute for these diodes other known suitable gating means, such for instance, as dry rectifiers or the like.

As far as the utility of the present invention is concerned, while it has been disclosed herein as embodied in a decimal or decade counter circuit arrangement, it will be apparent to those skilled in the art that the invention may be applied within its spirit and scope to other similar circuit arrangements, such as binary counters, digital computer circuits, etc.

It is to be understood that the above-described arrangements are merely illustrative of the application of the principles of the invention. Numerous other arrangements may be devised by those skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

1. In a signaling system, a source of pulses, a first electron discharge device, means controlled by said source for altering the normal conduction condition of said first device in response to a pulse, step-by-step counting means, means responsive to the change in the conduction condition in said first device for advancing said counting means a step to count said pulse, a second electron discharge device, means controlled by said counting means for altering the normal conduction condition of said second device in response to the advance of said counting means, time delay means, a third electron discharge device, means including said delay means and controlled during the altered condition only of said first device for altering the normal conduction condition of said third device a measured time after the normal condition of said first device is altered, means controlled by said altered condition of said second device for reestablishing the normal condition of said first device, and means for detecting the condition of said third device.

2. In a signaling system, a source of pulses, a first electron discharge device, means controlled by said source for causing conduction in said first device in response to a pulse, step-bystep counting means, means responsive to conduction in said first device for advancing said counting means a step to count said pulse, a second electron discharge device, means controlled by said counting means for causing conduction in said second device in response to the advance of said counting means, time delay means, a third electron discharge device, means accents includingsaid delay means. and controlled; during the conducting conditionronly; in said first device for causing conduction in said; third' device a measured time after conductionis .caused in said first device, means controlled by: conduce tion I in saidsecond device for stopping. conduction insaid first device, and means for detecting the condition of said third device:

3'. Ina signaling system, a source of pulses, a first gaseous discharge device, means controlled by said source for firing said first device in response to a, pulse,,step-by step counting means, means responsive to the firingof said first, device for advancing said counting means a step to count said pulse, a second gaseous discharge device, means controlled by'said counting means for firing said second device inresponse: to the advance of said counting means, time. delay means, a. third gaseous discharge device, means including said delay means and controlled during the firing condition only of said first device for firing said third device a measured time after the firing of said first device, means controlled by the firing of said second device for extinguishing said first device, and means for detecting the condition of said third device.

4. In a signaling system, a source of pulses, a first gas discharge tube, means controlled by said source for firing said first tube in response to a pulse, step-by-step counting means, means responsive to the firing of said first tube for advancing said counting means a step to count said pulse, a second gas discharge tube, means controlled by said counting means for firing said second tube in response to the advance of said counting means, a condenser, a third gas discharge tube, means including said condenser and controlled during the firing condition only of said first tube for firing said third tube a measured time after the firing of first tube, means controlled by the firing of said second tube for extinguishing said first tube, and means for detecting whether or not said third tube is fired before said first tube is extinguished.

5. In a signaling system, a source of pulses, a first gas discharge tube having a starter electrode circuit, means including said starter electrode circuit and controlled by said source for firing said first tube in response to a pulse, stepby-step counting means, means responsive to the firing of said first tube for advancing said counting means a step to count said pulse, a second gas discharge tube having a starter electrode circuit, means including said starter electrode circuit of said second tube and controlled by said counting means for firing said second tube in response to the advance of said counting means, a condenser, a charging circuit for said condenser, a third gas discharge tube having a starter electrode, circuit, means including said condenser and said charging circuit and controlled during the firing condition only of said first tube for charging said condenser to a potential which will fire said third tube a measured time after the firing of said first tube, means controlled by the firing of said second tube for extinguishing said first tube thereby to discharge said condenser, and means for detecting whether or not said third tube is fired before said first tube is extinguished.

6. In a signaling system, a source of pulses, a first gas discharge tube having a starter anode circuit, means including said starter anode circuit and controlled by said source for firing said first tube in response to each pulse, step-by-step counting means, means responsive to the firing of said first tube for advancing; saidcounting means astep for each pulse, a second gasdischarge tube having a starteraanode circuit, means including said starter anode circuit. of saidlsec- 0nd tube andlcontrolledi by; said counting means for firing saidsecond tube once inqresponseto cash advance ofisaid counting; means, 31.6011? denser, atime delay charging circuitfor said con denser,- a third gas. ischarge tube having a starter anode circuit, means including said condenser: and saidcharging circuit. and controlled during. each. firing only of said first: tube for charging said condenser to a potential whichwill fire said third tube: a measured time after each firing-of said first tube, means controlled by each of said'second tube foreXtinguishing-said first tube therebyto discharge said:- condenser, and means for detecting: whether or not said third tube is fired before said first tube is extinguished.

'7. In a signaling system, a chain of gas tubes for counting generated pulses, means including a gas tube which is rendered conducting for generating pulses, means for applying said generated pulses to said chain, the first pulse causing conduction in the first tube of said chain, commutating means interposed between tubes of said chain whereby successive tubes of said chain are rendered responsive to succeeding pulses, a check gas tube rendered conducting each time a succeeding tube of said chain is rendered conducting, said check tube operative when rendered conducting to render said generating tube nonconducting, a trouble gas tube rendered conducting after a time interval while said generating tube is conducting, and alarm means operated if conduction occurs in said trouble tube before conduction occurs in said check tube.

8. In a signaling system, a chain of gas tubes for counting generated pulses, means including a gas tube which is rendered conducting for generating pulses, means for applying said generated pulses to said chain, the first pulse causing. conduction in the first tube of said chain, commutating means interposed between tubes of said chain whereby successive tubes of said chain are rendered responsive to succeeding pulses, a check gas tube rendered conducting each time a succeeding tube of said chain is rendered conducting, said check tube operative when rendered conducting to render said generating tube nonconducting, a trouble gas tube, time delay means, said trouble tube rendered conducting through the agency of said time delay means after a timed interval while said generating tube is conducting, and alarm means operated if conduction occurs in said trouble tube before conduction occurs in said check tube.

9. In a signaling system, a chain of gas tubes for counting generated pulses, means including a gas tube which is rendered conducting for generating pulses, means for applying said generated pulses to said chain, the first pulse causing conduction in the first tube of said chain, commutating means interposed between tubes of said chain whereby successive tubes of said chain are rendered responsive to succeeding pulses, a check gas tube rendered conducting each time a succeeding tube of said chain is rendered conducting, said check tube operative when rendered conducting to render said generating tube nonconducting, a trouble gas tube, a condenser, a time delay charging circuit for said condenser, said condenser arranged to acquire a charge 19 from said generating tube through said charging circuit while said generating tube is conducting, and alarm means operated if conduction occurs in said trouble tube before conduction occurs in said check tube.

10. In a signaling system, a chain of gas tubes for counting generated pulses, means including a gas tube which is rendered conducting for generating pulses, means for applying said genera-ted pulses to said chain, the first pulse causing conduction in the first tube of said chain, commutating means interposed between tubes of said chain whereby successive tubes of said chain are rendered responsive to succeeding pulses, a check gas tube rendered conducting each time a succeeding tube of said chain is rendered conducting, said check tube operative when rendered conducting to render said generating tube non-conducting. atrouble gas tube, a condenser, a time delay REFERENCES CITED The following references are of record in the file of this patent: V

UNITED STATES PATENTS Number Name Date 1,726,009 White Aug. 27, 1929 2,589,465 Weiner Mar. 18, 1952 2,597,428 Bachelet May 20, 1952 

